Matsumoto in U.S. Pat. Nos. 4,164,755 and 4,165,560 discloses a pickup stylus for use with a capacitive information disc. The stylus is fabricated from a tapered diamond support element having a plurality of conical portions with a common axis. Two of the conical portions are separated by an electrode-bearing surface. A record-engaging surface is provided in a tip region substantially orthogonal to the electrode-bearing surface. The diamond support element includes a pair of converging flat surfaces in the tip region which are disposed such that the intersection of the converging flat surfaces with the record-engaging surface defines the side edges of the record-engaging surface. The intersection of the converging flat surfaces with a conical portion remote from the electrode-bearing surface forms a prow.
The stylus taught by Matsumoto may be manufactured by grinding a conical surface at one end of the diamond element. An electrode-bearing surface is formed in the region of the conical tip and a record-engaging surface is made substantially orthogonal to the electrode-bearing surface. A pair of converging substantially flat rear surfaces are also formed in the region of the tip such that the intersection of the converging flat surfaces with the record-engaging surface defines the sides of said record-engaging surface.
Keizer in U.S. Pat. Nos. 4,104,832 and 4,162,510 has disclosed a capacitive information system keel-tipped playback stylus. The terminating portion of the tip is shaped to have a prow, a substantialy flat rear surface remote from the prow, a pair of substantially parallel side surfaces extending from the side edges of the rear surface, a bottom surface extending from the bottom edge of the rear surface, and additional surfaces extending from the prow intersecting the bottom and side surfaces.
The keel-tipped stylus may be formed with an abrasive lapping disc having a deep, coarse-pitched groove. The tip is fabricated from a tapering support element having a tip which is defined by a prow and a substantially flat "V"-shaped rear surface remote from the prow. The lands of the lapping disc lap shoulders for the stylus. The walls of the abrasive groove form the substantially parallel side surface.
In order to reduce the cost of manufacturing a capacitive information disc playback stylus, it is advantageous to have dielectric support elements mounted on a shank, for example, a metal such as titanium. Such starting materials are common in audio stylus. Audio styli often have a conical-shaped tip. However, since the width of the information track on a capacitive information disc record is substantially smaller than the information track recorded in an audio record, the shanked dielectric support element must be appropriately shaped. It would, therefore, be desirable to have inexpensive means for converting a shanked dielectric support element to a relatively low cost capacitive information disc playback stylus.